It is desirable in modern construction practice that operable windows be installed in buildings, which windows are weatherproof, durable in operation, aesthetically pleasing and economical in terms of the production, installation and maintenance cost of same.
It is common in the prior art for windows, particularly institutional or commercial windows, to consist of a fixed frame and a swinging sash, with the frame and sash being constructed in part from components of extruded metal, such as aluminum, for reasons of strength and economy.
It is also known in the prior art for continuous hinge mechanisms of the pin and socket type to be utilized, for strength and esthetic reasons.
Further, it is known in the prior art for the pin and socket of such a continuous hinge to be incorporated as part of a window assembly. Examples of such prior art, with the pin incorporated into the sash and the socket incorporated into the frame, are shown in U.S. Pat. No. 2,845,665 (Place), issued Apr. 2, 1956, U.S. Pat. No. 3,908,313 (Bierlich), issued Sep. 30, 1975, and U.S. Pat. No. 4,175,357 (Goldhaber), issued Nov. 27, 1979.
However, known prior art window assemblies having hinge mechanisms of the continuous pin and socket type are known to fail as a result of the stresses created upon the hinge mechanism. Moreover, such known prior art window assemblies suffer, inter alia, from unduly high production, installation and maintenance costs, undue complexity of assembly, ranges of free rotation unsuitable for normal use, and undue weight and bulk.
In prior art window assemblies of this type, when the swinging sash has pivoted to the limit of its free rotation about the pin, the application of additional force typically results in stresses being placed upon the hinge socket. Such stresses can result in inelastic distortion of the components of the hinge, and the creation of clearance between the pin and socket, with adverse effect upon the operation of the mechanism; for example, looseness in the hinge mechanism, which enables the window to rattle in its frame. As well, failure of the weatherproofing can result.
In addition, forces are typically created in prior art hinge of this general type in a direction oriented to displace the pin from the socket. As a result, where the shape of the socket has become distorted as mentioned, the pin can actually breach the socket, allowing the swinging sash to become operatively disconnected from the frame.
The risk of the swinging sash becoming disconnected can be lessened by decreasing the width of the aperture in the socket, since, all other things being equal, the amount of force required to displace the pin from the socket is thereby increased; however, this solution to the problem has a corresponding negative impact upon the free range of rotation of the sash, and is not favoured.
Similarly, the substitution of another material as the socket substrate, which material is also resistant to corrosion but stronger than aluminum, can also increase the amount of force required to displace the pin from the socket; known alternative materials, however, such as stainless steel, are uneconomic, both in terms of the raw material cost and the costs related to manufacture, as aluminum is particularly well-suited to processing through the low cost extrusion process.
Therefore, the aforementioned problems are typically overcome in the prior art by one or more of the following methodologies: (a) increasing the thickness of the socket material to increase rigidity, such that additional force is required to be exerted before the socket distorts; and, (b) constructing suitably robust external means to arrest the swinging sash in its rotation before it reaches the limit of its free range of motion.
While either of these solutions may resolve to some extent the problems associated with prior art hinges of the general type under consideration, each of these solutions necessarily cause the cost of production and installation of the window and sash assembly to increase. Moreover, in some cases, these solutions increase the bulk and weight of the window assembly to unacceptable levels, or are aesthetically unpleasing.
Similar problems exist in prior art windows when the pin is incorporated into the frame and the socket into the swinging sash. U.S. Pat. No. 4,084,361 (Aspaas), issued Apr. 18, 1978, shows a window assembly of this type intended for pivotal opening about a vertical axis. In addition to the problem of the stresses placed upon the hinge mechanism, this design also suffers from the requirement that suitable weatherstripping be incorporated about the hinge mechanism to avoid infiltration of moisture and debris, the weatherstripping being in an area exposed to weather. The need for weatherstripping adds to the cost of production of the window assembly, and the location of the weatherstripping in the design results in further costs due to required maintenance.
U.S. Pat. No. 2,797,778 (Wagner), issued Jul. 2, 1957, is an example of the prior art which attempts to resolve the problem of the aforementioned stresses which can be created when the sash has pivoted to the limit of its rotation by employing co-operating spiral flanges to form the hinge mechanism. In this design, the limit of rotation is almost a full 360.degree., well outside the range of motion required for normal window installations. The Wagner design, however, suffers from an inherent drawback in that, as the radius of a spiral increases (or decreases) gradually throughout its length, there can be no free range of motion in a hinge mechanism incorporating co-operating spiral components. At any given point of contact between the spiral components, rotation of one spiral with respect to the other brings into contact points of different radius, thereby causing one or both of the spirals to expand or contract at the point of contact. Depending upon the torsional rigidity of the construction medium of the spiral flanges and the nature of their construction, this can result in the need to apply significant force to effect rotation. This problem is exacerbated by the additional surface area such a spiral hinge exposes to friction, further increasing the force required to effect rotation. The problem of high rotational force can be resolved, in part, by the incorporation of lubricating material, such as tetrafluorethylene, between the co-operating flanges, which material adds to the cost of construction, or alternatively, the provision of clearance, which results in a hinge without controlled smooth operation.
U.S. Pat. No. 3,802,127 (Silvernail), issued Apr. 9, 1974, illustrates a further attempt in the prior art to overcome the subject stresses. In the Silvernail patent, a bead positioned on the smaller arm of an inverted J-shaped member pivots in a groove and provides the pivoting mechanism for the window. This design resolves the issues of the subject stresses to a limited extent, as, at the limit of rotation, the application of additional opening force on the window sash will not tend to distort the socket. In this design, however, the bead portion will still become subject to stresses tending to unseat it from the groove. Moreover, the Silvernail patent requires weatherstripping at two locations within the hinge mechanism and requires an external flash guard/drip rail to protect the mechanism from water and debris infiltration. Further, the Silvernail device requires a separate bulky plastic component wherein the groove is located. All of these factors add to the cost of production and maintenance of the Silvernail assembly.